Adhesion Theory for Low Friction on Ice

AbstractThe friction behavior of metals is directly linked to the mechanisms that accommodate deformation. We examine the links between mechanisms of strengthening, deformation, and the wide range of friction behaviors that are exhibited by shearing metal interfaces. Specifically, the focus is on understanding the shear strength of nanocrystalline and nanostructured metals, and conditions that lead to low friction coefficients. Grain boundary sliding and the breakdown of Hall–Petch strengthening at the shearing interface are found to generally and predictably explain the low friction of these materials. While the following is meant to serve as a general discussion of the strength of metals in the context of tribological applications, one important conclusion is that tribological research methods also provide opportunities for probing the fundamental properties and deformation mechanisms of metals.

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Anomalously low friction of confined monolayer water with a quadrilateral structure

The Journal of Chemical Physics ◽

10.1063/5.0053361 ◽

2021 ◽

Vol 154 (22) ◽

pp. 224508

Author(s):

JinChuan Li ◽

YinBo Zhu ◽

Jun Xia ◽

JingCun Fan ◽

HengAn Wu ◽

...

Keyword(s):

Low Friction

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Comparative Analysis of Periodontal Pain According to the Type of Precision Orthodontic Appliances: Vestibular, Lingual and Aligners. A Prospective Clinical Study

Biology ◽

10.3390/biology10050379 ◽

2021 ◽

Vol 10 (5) ◽

pp. 379

Author(s):

Laura Antonio-Zancajo ◽

Javier Montero ◽

Daniele Garcovich ◽

Mario Alvarado-Lorenzo ◽

Alberto Albaladejo ◽

...

Keyword(s):

Clinical Study ◽

Pain Intensity ◽

Short Form ◽

Study Groups ◽

Mcgill Pain Questionnaire ◽

Prospective Clinical Study ◽

Orthodontic Appliances ◽

Low Friction ◽

Different Types ◽

Lower Arch

The objective of this prospective clinical study was to analyze the pain (intensity, location and type) that patients presented after the placement of different types of orthodontic appliances: conventional, low friction, lingual and aligners. The sample consisted of 120 patients divided into four groups: conventional (CON), low friction (LF), lingual (LO) and aligners (INV). The participants were given the Short-Form McGill Pain Questionnaire (Ortho-SF-MPQ), where they had to record the pain intensity (no pain, mild, moderate or intense) and the periodontal location at different time points, from the first 4 h to 7 days after the start of treatment. In all the study groups, the most frequent location was both anterior arches, with maximum values between 56.7% (CON group at 24 h) and 30% (LO group at 4 h). The “whole mouth” and “complete lower arch” locations were indicated only by the patients in the lingual group. Regarding pain intensity, the patients reported a higher percentage of mild–moderate pain during the first 3 days of treatment (96.7% in LO at 4 h, 86.7% in CON, 83.3% in LF and 90% in INV at 24 h); later, the reported pain decreased to no pain/mild pain, especially in the lingual group, until reaching values close to zero at 7 days post-treatment. The most frequent type of pain was acute in the low friction and lingual groups (with maxima of 60% and 46.7% at 24 h, respectively). On the contrary, in the conventional (36.7% at 4 h) and Invisalign (40% at 24 h) groups, the sensitive type was the most frequent. There are differences regarding periodontal pain in its intensity, location and type according to the use of different orthodontic techniques.

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